Bad examples leads to bad developers

[sirian]

1. Destructive assignment in this simple case?

 function resetBoard() {
    [hasFlippedCard, lockBoard] = [false, false];
    [firstCard, secondCard] = [null, null];
  }

Easily replaces with

 function resetBoard() {
    hasFlippedCard =  lockBoard = false;
    firstCard = secondCard = null
  }

2. Shuffle is incorrect

Code flow: shuffle is not uniform

Try to count how often vue turns out on top-left card

Code style

(function shuffle() {
    cards.forEach(card => {
      let ramdomPos = Math.floor(Math.random() * 12);
      card.style.order = ramdomPos;
    });
  })();

let should be replaced with const
12 should be replaced with cards.length
moreover why you use IIFE here? you could simply write

// shuffle elements
cards.forEach(card => {
    const ramdomPos = Math.floor(Math.random() * cards.length); 
    card.style.order = ramdomPos;
});

3. It is a de-facto standard to use brackets in if statements (even in one-liners)

if (lockBoard) {return;}
if (this === firstCard) {return;}

And there are plenty more...